Assessment of Plug-in Electric Vehicle on Distribution ...Assessment of Plug-in Electric Vehicles Charging on Distribution Networks Master Thesis Defense - Tsz Kin (Marco) Au Committee

Assessment of Plug-in Electric Vehicles Charging on Distribution Networks

Master Thesis Defense - Tsz Kin (Marco) Au

Committee Chair: Dr. M. Ortega-Vazquez Committee Co-Chair: Dr. M. El-Sharkawi Committee Member: Dr. D. Kirschen

Presentation Outline

I. Introduction of PEV

II. The developed tool for investigating the impact of PEV

III. Test system characteristic

IV. Test result

V. Conclusion

6/5/2012 Electrical Engineering Department - University of Washington

Master Thesis Defense - Tsz Kin (Marco) Au 2





IV. Test result

V. Conclusion



Technological Impacts of PEVs

Potential benefits: • Lower operating cost than combustion engine vehicles: 3.7 vs. 16.7 cents

• On road CO2 emission will be lower

• V2G and ancillary services provide business opportunities

Problems: • 10% penetration = additional 300 GWh per day in the U.S.

• Increase grid losses

• Reduce system spare generation and harder to schedule maintenance

• Poorer voltage profile and transformer overloading in weakly meshed distribution networks

6/5/2012

Electrical Engineering Department - University of Washington Master Thesis Defense - Tsz Kin (Marco) Au

4

What causes poor voltage profile and transformer overloading?



Line impedance

Coincidence between PEV charge time and system peak load

Lack of interconnection

Poor voltage profile and overload

transformer





IV. Test result

V. Conclusion



Monte Carlo Simulation

• Suitable for analysis when uncertainties present

• 4 uncertainties needed to be address: – Charging time

– Battery state of charge (SOC)

– Charging method

– Customer load variation

• 7 major functional blocks

• Each trail represent 24 hours



Read data and initialize parameters

Generate random scenarios

Run deterministic system

1. Data Processing and Initialization

• 34,000+ drivers’ behavior from CMAP, which consists of their to-work and to-home arrival times.

• Electric vehicle parameters – Battery capacity

– Energy consumption per unit distance

• Distribution network conductor parameters

• Average power consumption and load type at each node – Residential area

– Commercial area



2. PEV Penetration and Charging Points

𝑃𝐸𝑉 𝑃𝑒𝑛𝑒𝑡𝑟𝑎𝑡𝑖𝑜𝑛 =𝑇𝑜𝑡𝑎𝑙 𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑝𝑎𝑠𝑠𝑒𝑛𝑔𝑒𝑟 𝑃𝐸𝑉

𝑇𝑜𝑡𝑎𝑙 𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑝𝑎𝑠𝑠𝑒𝑛𝑔𝑒𝑟 𝑣𝑒𝑕𝑖𝑐𝑙𝑒𝑠



66.67%

33.33%

Charge at home or at work? Type 1: Charge at home only Type 2: Charge at home and work

3. PEV’s Arrival Time

• PEV drivers will charge their vehicles anytime at their convenience

• Their arrival times affect the charge profile

• Drivers’ behaviors varies from day to day, which creates uncertainty

• Must model the uncertainty in order to simulate its effect to the power system



3. PEV’s Arrival Time

Inverse transformation for random number generation

• Map rand(0,1) → actual distribution



4. PEV’s Battery State of Charge

• Commute distance have an effect on the battery state of charge

• A driver’s commute distance although is similar everyday, it may vary sometime, which causes uncertainty

• Must model this uncertainty in order to simulate its effect to the power system

• Convert commute distance to battery state of charge (SOC) 𝑆𝑂𝐶 = 𝐵𝑎𝑡𝑡𝑒𝑟𝑦 𝐶𝑎𝑝. (𝑘𝑊𝑕) − 𝐶𝑜𝑚𝑚𝑢𝑡𝑒 𝐷𝑖𝑠𝑡. (𝑚𝑖𝑙𝑒) × 0.34 𝑘𝑊𝑕/𝑚𝑖𝑙𝑒



4. PEV’s Battery State of Charge



Commute distance (miles) Percentage (%) 0 – 4.0 19.19

4.1 – 8.0 22.95

8.1 – 12.0 16.67

12.1 – 16.0 13.77

16.1 – 20.6 9.37

20.1 – 24.0 6.07

24.1 – 28.0 4.59

28.1 – 32.0 2.69

32.1 + 4.70

0

5

10

15

20

25

Pe

rce

nta

ge (

%)

Commute Distance (Mile)

Commute Distance Distribution

y = 353.04x5 - 725.13x4 + 526.87x3 - 140.15x2 + 22.691x - 0.0038

R² = 0.9997

-5

0

5

10

15

20

25

30

35

0 0.2 0.4 0.6 0.8 1

Co

mm

ute

Dis

tan

ce (

Mile

) Probability

Quantile Function of Commute Distance

5. PEV Charge Profile

• Computed individually based on arrival time, battery state of charge, and charging method

𝑇𝑜𝑡𝑎𝑙 𝐶𝑕𝑎𝑟𝑔𝑒 𝑃𝑟𝑜𝑓𝑖𝑙𝑒𝑕𝑟 = 𝑃𝑖,𝑕𝑟

# 𝑜𝑓 𝑃𝐸𝑉

𝑖



0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 300

2

4

6

8

Hour

Pow

er

(kW

)

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 300

2

4

6

8

Hour

Pow

er

(kW

)

6. Customer Load Profile

• Varies from day to day

• The variation is assumed to be Gaussian distributed:



𝑓 𝑃𝑏𝑢𝑠,𝑡𝑖 = 1

𝜎𝑏𝑢𝑠,𝑡𝑖 2𝜋𝑒−12∙(𝑃𝑏𝑢𝑠,𝑡𝑖−𝐴𝑣𝑔𝑃𝑏𝑢𝑠,𝑡𝑖)

𝜎𝑏𝑢𝑠,𝑡𝑖2

𝐴𝑣𝑔𝑃𝑏𝑢𝑠,𝑡𝑖 = 𝑃𝑡𝑦𝑝𝑒,𝑡𝑖𝑛𝑜𝑟𝑚 × 𝐴𝑣𝑔𝑃𝑏𝑢𝑠

7. Running Power Flow Analysis for the Distribution System

• Cannot use Newton-Raphson based methods

• Distribution networks characteristic: – High R/X ratio → Decoupled and fast decoupled methods won’t work

– Weakly meshed, sparse network → Newton-Raphson method won’t work

• Forward-backward sweep method is used






Forward-backward sweep method example:

𝑧 = 0.3 + 𝑗0.6 Ω/𝑚𝑖𝑙𝑒 𝑧12 = 0.1705 + 𝑗0.3409 Ω 𝑧23 = 0.2273 + 𝑗0.4545 Ω

𝑠2 = 1500 + 𝑗750 𝑘𝑊 + 𝑗𝑘𝑉𝑎𝑟 𝑠3 = 900 + 𝑗500 𝑘𝑊 + 𝑗𝑘𝑉𝑎𝑟

1 2 3

S2 S3

3000’ 4000’

7200V





1 2 3

S2 S3

3000’ 4000’

7200V

Forward sweep:

1) Assume voltage at node 3 is 7200V

2) Compute 𝐼3

𝐼3 =𝑠3𝑉3

∗

= 143.0∠ − 29.0 𝐴

𝑉3 = 7200 𝑉

𝐼23

3) Compute 𝐼23 𝐼23 = 𝐼3 = 143.0∠ − 29.0 𝐴

𝐼3

4) Compute 𝑉2 𝑉2 = 𝑉3 + 𝑍23 ∙ 𝐼23 = 7260.1∠0.23 𝑉

5) Compute 𝐼2

𝐼2 =𝑠2𝑉2

∗

= 231.0∠ − 26.3 𝐴

6) Compute 𝐼12 𝐼12 = 𝐼23 + 𝐼2 = 373.9∠ − 27.3 𝐴

7) Compute 𝑉1 𝑉1 = 𝑉2 + 𝑍12 ∙ 𝐼12 = 7376.2∠0.97 𝑉

8) Compute mismatch between 𝑉1and 𝑉𝑠

𝑀𝑖𝑠𝑚𝑎𝑡𝑐𝑕 = 𝑉𝑠 − 𝑉1 = 176.2 𝑉

𝐼12

𝐼2

𝑉2 = 7260∠0.23 𝑉 𝑉1 = 7376.2∠0.97 𝑉

Not satisfy!





1 2 3

S2 S3

3000’ 4000’

7200V

Backward sweep:

1) Assume voltage at node 1 is 7200V, and use the line currents computed from forward sweep

2) Compute 𝑉2 𝑉2 = 𝑉1 − 𝑍12 ∙ 𝐼12 = 7085.4∠ − 0.68 𝑉

𝑉3 = 7026.0∠ − 1.02 𝑉

𝐼23 𝐼12

𝑉2 = 7085.4∠ − 0.68 𝑉 𝑉1 = 7200 𝑉

3) Compute 𝑉3 𝑉3 = 𝑉2 − 𝑍23 ∙ 𝐼23 = 7026.0∠ − 1.02 𝑉





1 2 3

S2 S3

3000’ 4000’

7200V

Perform forward sweep again:

1) Use the voltage at node 3 from the backward sweep

2) Compute 𝐼3

𝐼3 =𝑠3𝑉3

∗

= 146.5∠ − 30.1 𝐴

𝑉3 = 7026.0∠ − 1.02 𝑉

𝐼23

3) Compute 𝐼23 𝐼23 = 𝐼3 = 146.5∠ − 30.1 𝐴

𝐼3

4) Compute 𝑉2 𝑉2 = 𝑉3 + 𝑍23 ∙ 𝐼23 = 7087.6∠ − 1.02 𝑉

5) Compute 𝐼2

𝐼2 =𝑠2𝑉2

∗

= 236.6∠ − 27.2 𝐴

6) Compute 𝐼12 𝐼12 = 𝐼23 + 𝐼2 = 383.0∠ − 28.3 𝐴

7) Compute 𝑉1 𝑉1 = 𝑉2 + 𝑍12 ∙ 𝐼12 = 7206.5∠0.0 𝑉

8) Compute mismatch between 𝑉1and 𝑉𝑠

𝑀𝑖𝑠𝑚𝑎𝑡𝑐𝑕 = 𝑉𝑠 − 𝑉1 = 6.535 𝑉

𝐼12

𝐼2

𝑉2 = 7087.6∠ − 1.02 𝑉 𝑉1 = 7206.5∠0.0 𝑉

Satisfy!





IV. Test result

V. Conclusion



Test System Characteristic

Assumption:

• 4000 residents

• Average 2.35 people and 1.78 passenger vehicles per household

• power factor = 0.9

• power factor = 0.8

• Avg. 959.5 W/household

• Average power consumption:



= residential area = 85 households

= commercial area = 1 small shopping plaza

= 81.6 + 40.8j (kW+kVar)

= 100 + 75j (kW+kVar)

Test System Characteristic

Charging method and scenario:

• Level 1: 1.3 kW

• Level 2: 3.3 kW

• Level 3: 50 kW



75%

25%

Type 1

Level 1

Level 2

Level 3

85%

15%

Type 2a (charge at residential area)

Level 1

Level 2

Level 3

60% 30%

10%

Type 2b (charge at commercial area)

Level 1

Level 2

Level 3





IV. Test result

V. Conclusion



Test Result: Voltage Violation

Voltage Profile

• Voltage should operate ±0.05 p.u.

• Voltages at the End Buses have higher chance to suffer low voltage violation






Voltage profile confidence interval at bus 16

0% Penetration 30% Penetration

50% Penetration 100% Penetration




Voltage distribution for 0% Penetration Scenario









Test Result: Transformer Load

• Although transforms usually can be overloaded for short period of time with limited amount, overloading it by too much or too long will decrease its life time

• Transformer overloaded: loaded above its capacity

• Transformer violation: loaded 20% above its capacity



Test Result: Transformer Load



Transformer load profile Transformer load distribution





IV. Test result

V. Conclusion



Conclusion

• Electricity for transportation? Yes or No?

• PEVs impacts vary from system to system – Voltage violation: long radial networks

– Substation transformer violation: Heavy load, high PEV penetration

• A tool to evaluate PEVs impacts is developed



Thank you!



Assessment of Plug-in Electric Vehicle on Distribution ...Assessment of Plug-in Electric Vehicles Charging on Distribution Networks Master Thesis Defense - Tsz Kin (Marco) Au Committee

Documents